Undergraduate Honors Theses

Thesis Defended

Spring 2013

Document Type



Ecology and Evolutionary Biology

First Advisor

Valerie McKenzie


The American bullfrog, Lithobates catesbeianus, is a well-established invasive species found throughout the world. While means and implications of introduction are well studied, reasons behind successful establishment of invasive bullfrogs are not well known. In order to address whether a release from natural enemies may be behind successful bullfrog invasion, we examined parasite species abundance and diversity of bullfrog populations. A dataset of bullfrog parasites from 22 locations was compiled through (i) firsthand collection from bullfrog dissections and (ii) a literature review. We examined the effects of latitude, host range (native versus invasive), and distance from the native range as site level predictors for the variance in parasite richness (number of different species represented) per site and sum prevalence (total percentage of the individual parasite species observed), respectively. While parasite richness was not significantly different between the native and invasive ranges, GLM analysis demonstrated that the biogeographic factors latitude and distance from the native range together predicted variability in parasite species richness, but not sum prevalence. Parasite species richness increased with increased latitude and decrease with increased distance from the native range. Difference in abundance of direct and complex life cycle parasites (infecting a single species versus infecting more than one host species) between ranges was marginally significant. Since the success of invasive bullfrogs may be related to a release from natural parasite enemies, understanding patterns of species diversity and the influence of biogeographic factors on parasite richness could help predict the probability and intensity of bullfrog invasions.